A typical insulating glass (IG) unit is generally comprised of two panes of glass separated by a metal spacer (also referred to as a spacer frame) that holds the two glass panes together, forming an insulating space therebetween. An insulating gas (e.g., argon, krypton, etc.) is injected into the insulating space between the two glass panes to provide the IG unit with desired insulating properties. One or two gas filling holes may be provided in the spacer that separates the two glass panes to facilitate filing of the insulating space with insulating gas.
The process of filling an IG unit with insulating gas can be a slow process, the speed of which is influenced by how quickly the volume of gas in the IG unit can be exhausted. Gas filling is done by one of two methods, namely, laminar or dilution filling.
Laminar filling is a method of filling the insulating space of the IG unit with insulating gas by means of a laminar flow. Two holes are needed in the spacer that is located between the two panes of glass, i.e., one hole located at the bottom of the spacer and one hole located at the top of the spacer. Insulating gas is injected through the bottom hole of the spacer in a laminar flow that induces a boundary layer between the insulating gas and the air located in the insulating space. As the insulating gas (which is heavier than air) fills the insulating space, it displaces the air that exits through the top hole of the spacer. The rate at which the insulating gas can be injected into the insulating space is determined by how fast air can be exhausted from the insulating space, as limited by a filling speed that prevents excess turbulence that will disrupt the laminar nature of the gas flow. A sensor “sniffs” the air and gas exhausted from the insulating space through the top hole to determine an insulating gas concentration. When the sensed insulating gas concentration reaches a predetermined concentration, the gas filling cycle ends.
Dilution filling is a method of filling the insulating space of the IG unit with insulating gas by injecting the insulating gas at a high fill rate that causes the insulating gas to mix with the air inside the insulating space, and exchange the air inside the insulating space with the insulating gas. Typically, dilution filling is done with a single hole located at the top of the spacer. By inserting the insulating gas into the insulating space through the hole in the top of the spacer, the insulating gas mixes with the air inside the insulating space. A sensor “sniffs” an insulating gas/air mixture exhausted from the insulating space through the hole in the spacer to determine the insulating gas concentration. When the insulating gas concentration reaches a required concentration, the gas filling cycle ends. Since dilution filling results in the mixing of the insulating gas and air inside the insulating space there is a significant waste of insulating gas. In this respect, it is usually necessary to fill the insulating space with a volume of insulating gas that is at least three times the volume of the insulating space in order to reach the required insulating gas concentration exhausted from the insulating space.
With each of the above-described gas filling methods, the determining factor of how fast an insulating space can be filled is related to how quickly the insulating gas can be injected into the insulating space. Although insulating gas can be inserted faster using the dilution filling method, as compared to the laminar filling method, the insulating gas can only be inserted as quickly as the gas/air mixture can be exhausted from the insulating space through the exhaust hole. A vacuum pump can be used assist to exhaust the gas/air mixture from the insulating space. In this respect, the vacuum pump induces a vacuum at the exhaust hole to draw the gas/air mixture out of the insulating space at an increased flow rate. With an increased flow rate for exhausting the gas/air mixture, the gas insertion flow rate can be increased. However, even with a perfect vacuum, the rate at which the gas/air mixture is exhausted from the insulating space is limited by the orifice size of the exhaust hole.
Holes are typically formed in a spacer by punching or drilling a 3 mm or 4 mm diameter round hole, depending upon the size/width of the spacer. The size of the hole is limited by the size/width of the spacer. Smaller spacer widths do not accommodate a larger hole, because the hole will consume most of the spacer width and decrease the structural integrity of the spacer. Larger sized holes can be punched/drilled, but only on wider spacers. However, since tooling is not easily changed, manufacturers typically select a hole size based on the smallest sized spacer being used. Thus, it is estimated that more than 95% of manufacturers currently employ tooling having a 3 mm or 4 mm diameter punch/drill. A much smaller percentage of manufacturers currently employ tooling providing a 5 mm diameter punch/drill to form 5 mm diameter round holes. Limits on hole size result in limits on the flow rate for exhausting air and gas from the insulating space.
In order to retain the insulating gas inside the insulating space after the filling process, it is necessary to properly seal the spacer hole(s). Currently, IG units are being commercially produced with spacers having conventional round gas filling holes, because plugs are known which close such spacer holes. These plugs serve multiple functions, namely, locking together the ends of an assembled spacer, and retaining the gas inside the insulating space in a marginally gas tight manner. At present, holes in the spacer are sealed with a plug taking the form of a screw or a closed end round rivet. Both of these types of plugs have drawbacks. In this respect, screws lack a reliable airtight seal, while rivets require special tools to install in the hole.
As a result of slow gas filling speeds, the gas filling step tends to become a bottleneck in the process of manufacturing IG units. These bottlenecks can become costly to manufacturers. To address this situation, manufacturers will often take a single flow of IG units off of a production line and route them through multiple gas filling stations. This is a labor intensive process, and a highly manual process, that is subject to quality and capacity variances.
The present invention provides a method and apparatus for filling and sealing insulating glass units that addresses these and other drawbacks currently existing in the field of IG unit manufacturing.